Astro optics pvt. Ltd. An iso 9001 : 2000 certified company manufactures various types of optical components and lenses are one of them. Astro optics pvt. Ltd. Presents a range of filters which are used to `filter` out light, which means to separate out wavelengths. Being a part of that color glass filters have a different transmission and absorption properties and are used for broadband spectral filtering. These are used as long pass and band pass filters. They are much less expensive than coated filters. Color glass filters are from schott and germany.